This disclosure relates generally to wireless communication systems, and in particular but not exclusively, relates to the use of a common aperture holographic optical element (HOE) devices for a free space optical transceiver.
At a basic level, a typical wireless optical telecommunication system comprises an optical transmitter and an optical receiver, with associated electronics to modulate and demodulate data on a light beam.
These optical transmitter and receiver units may have many parts, thereby contributing to the overall size or xe2x80x9cfootprintxe2x80x9d of the units. The individual parts themselves may also have a large footprint. This increased footprint can be detrimental in situations where the units need to be installed in a non-obtrusive manner. The increased footprint can also disadvantageously limit the amount of available space, within the housing of the transmitter or receiver units, in which to fit the various parts or components.
In an effort to reduce the overall footprint of these components, optical transmitters and optical receivers are sometimes combined together into optical xe2x80x9ctransceivers.xe2x80x9d However, despite some potential gain in compartmentalization as a result of this combination, other components nevertheless often need to be included with the optical transceiver in order to provide the optical transceiver with additional functionalities. Adding these other components for each type of functionality increases the overall complexity, costs, fragility, footprint and bulkiness of the transceiver. The components themselves, as well as the transceiver, are difficult to manufacture with consistent quality. Because optical communications systems are capable of much higher data rates than traditional radio frequency (RF) systems, stable and inexpensive transceivers that provide multiple-features are needed.
According to an aspect of the invention, an apparatus includes a first holographic optical element (HOE) device having a first recorded interference pattern to diffract a received light signal into a plurality of orders. A second HOE device has a second recorded interference pattern and is positioned relative to the first HOE device to reflect the orders of the diffracted light signal towards corresponding optical components. The first and second HOE devices have their interference patterns recorded on an emulsion material that is shaped to provide a common aperture through which to pass a transmitted light signal.